The combustion of liquid fuel, such as liquid hydrocarbons, is a standard method of power and/or heat generation. The combustion may be in a system where the heat is transferred to another medium, such as water, with or without boiling the water, or the fuel may be burned in various types of internal combustion engines, such as those operating on Otto, diesel, or other cycle. The amount of oxygen, usually air, is at least about theoretically sufficient for complete combustion of the fuel elements.
Considerable problems have arisen. If there is a very large excess of oxygen, the efficiency of the combustion process is lowered because a considerable amount of air, including inert nitrogen, has to be heated up. In the case of an internal combustion engine also operating with excessive excesses of oxygen can result in slow combustion, which can overheat and burn out exhaust valves. If the combustion is with amounts of oxygen and fuel more nearly in balance, for example with only a small excess of oxygen, problems arise with incomplete combustion. This can result in excessive amounts of carbon monoxide and/or incompletely burned fuel, which may show up as unburned hydrocarbons, soot, and the like. Incomplete combustion lowers the combustion efficiency and can also contaminate the equipment. In the case of internal combustion engines, unburned hydrocarbons, carbon monoxide, and oxides of nitrogen, generally symbolized by the formula NO.sub.x, are serious atmospheric pollutants as they give rise to photochemical smog and the like. Contamination of nitrogen oxides from an internal combustion engine usually results when combustion temperature is high.
It has been proposed in the past to introduce streams of water into a burner or to inject water into an internal combustion engine as it operates. This has proven to reduce somewhat incompletely burned fuel desposited in the form of carbon, and in the case of internal combustion engines this can lower nitrogen oxide production and also in certain cases, such as aircraft piston engines, permit operating for short times at higher power outputs with very rich mixtures which would otherwise burn up the engine. Water injection, however, has serious drawbacks.
Problems have arisen in the control of relative amounts of water and fuel precisely, and even if the control is maintained to a satisfactory degree, efficiency drops because the water has to be vaporized.
It has also been proposed to produce an emulsion of hydrocarbon fuel and water by sonic vibration and then to burn this emulsion in a burner. This is described, for example, in the U.S. Pat. to Duthion, No. 3,658,302, Apr. 25, 1972. The Duthion patent utilizes a form of sonic agitation produced by impinging a jet of the liquids against the edge of a blade free to vibrate. This form of sonic device is known in the art as a liquid whistle and was developed by the inventor of the present application, whose earliest U.S. Pat. is No. 2,657,032, Oct. 1953. While the emulsion produced is capable, in some cases, of being burned in a burner, particularly when a considerable amount of surfactant is added, it does not burn completely and produces an amount of heat which is usually less than that obtained by burning the fuel content because with the poor quality of emulsion the heat required to vaporize the water reduces the efficiency.
The present invention deals with an improved water-in-oil emulsion with which much higher efficiency is produced.